There's one big unknown on the Democratic side of this race. Who will be Hillary Clinton's running mate? The short list includes Labor Secretary Tom Perez and some senators - Sherrod Brown of Ohio, Elizabeth Warren of Massachusetts and Tim Kaine of Virginia. Tomorrow Clinton hits the campaign trail with Kaine. NPR congressional reporter Susan Davis visited the city Kaine calls home.

SUSAN DAVIS, BYLINE: On this rainy Thursday night, only a handful of choir members are out for weekly practice at St. Elizabeth's in Richmond.

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UNIDENTIFIED CHOIR: (Singing) Wade in the water. God's going to trouble the water.

DAVIS: Negro spirituals about the Underground Railroad aren't exactly commonplace at Catholic Churches. St. Elizabeth's is a predominantly black Catholic, and hanging in this church is a black Jesus, which wasn't uneasy Father Jim Arsenault recalls with a laugh.

JIM ARSENAULT: The Italians did not want to make Jesus black. I kept rejecting the color of the skin tone. And I said, you know, the community's kind of African-American. And I think that threw the Italians for a loop.

DAVIS: This church has been Tim Kaine's parish his entire adult life. He got married here. His three kids were baptized here. He was a parishioner before he ever ran for elected office, and he stayed a parishioner as politics drew him from the Richmond City Council to the mayor's office, from lieutenant governor to the governor's mansion and now as the state's junior senator.

He's no longer a regular at Thursday choir practice, but musical director Kim Ford says Kaine still makes appearances during Sunday mass, particularly when she needs a tenor.

KIM FORD: Tim sung in there until he really started kicking it with the politics and, you know, mayor and governor and so on, so forth. And then he - it took his time away from us a little bit. But when he comes here, I still snatch him out the audience.

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UNIDENTIFIED CHOIR: (Singing) ...The water.

DAVIS: Kaine was raised near Kansas City, Mo., but his political life was born here in Richmond. He ended up here because of his wife, Anne Holton. They met at Harvard. Viola Baskerville is a longtime Kaine ally. I met her for lunch at a restaurant across town from St. Elizabeth's. She says Anne helped shape Kaine's progressive views on race.

VIOLA BASKERVILLE: Knowing that she had been one of the students to integrate one of the early schools in the city of - public schools in the city of Richmond, I think some of those things really form meaningful relationships and impressions on you.

BASKERVILLE: Holton is the daughter of former Republican Governor Linwood Holton. He helped integrate the Virginia public school system, and he sent Anne and her siblings to black schools. This vein of racial equality pulses throughout Kaine's rise in Virginia and national politics, and it helps explain why he's a two-time Democratic contender for vice president.

As a young Richmond lawyer, Kaine focused on housing discrimination cases. His work within the black community helped fuel his first election victory to the city council in 1995. Baskerville served with Kaine on the Richmond City Council. She remembers that election.

BASKERVILLE: After he won, he held up his loafer that - he had a hole in the bottom of his loafers 'cause he had walked so much in the community. The African-American community very well respected him and very much supported him.

DAVIS: Kaine has never lost an election, and in every one of those elections, he's been able to win black voters without alienating whites and vice versa. That's hard to do in Southern politics where the racial divide is often widest on Election Day. In his runs for governor and Senate, Kaine performed well for a Democrat in traditional Republican strongholds. He's won with the vote of Virginians like Bob Mooney. He's a Richmond-based entrepreneur. If Clinton tops Kaine as her running mate, it would win his vote.

BOB MOONEY: That's the only way I would cast that vote.

DAVIS: Mooney helped build a Richmond magnate school named after Maggie Walker, the first black woman to run a bank in the U.S. Mooney says Kaine was one of the politicians that helped make it happen.

MOONEY: I just think he's a, you know, a person of tremendous values.

DAVIS: Those values are what prompted his early endorsement of then little-known Illinois Senator Barack Obama in 2007. Kaine was the first Democratic governor to back him. Mark Rubin was Kaine's attorney when he was governor. I met him at City Diner, one of Kaine's local hangouts.

MARK RUBIN: But the notion of having the first black president was a big deal to Tim, and so he jumped.

DAVIS: That support helped earn Kaine a place on Obama's short list in 2007. This time his supporters say that record on diversity and his cross-party appeal could help a candidate who is disliked by as many Americans as her opponent. Clinton could use some likeability, some might even say a choirboy.